A terminal fitting including a backing material made of Cu (copper) alloy and a Sn (tin) plating coating covering surfaces of the backing material is known as a terminal fitting used for the connection of an electrical circuit. Terminal fittings come in various modes such as fitting-type terminals to be crimped to ends of wires and board terminals to be mounted on circuit boards. These terminal fittings may be singly used or may be used by being incorporated into connectors.
A terminal material in which a Ni (nickel) plating layer, a Cu plating layer and a Sn plating layer are successively laminated on a surface of a Cu alloy base material is frequently used as a terminal material used for terminal fittings (patent literature 1 JP2003-147579). However, since the terminal described in patent literature 1 includes a relatively soft Sn plating layer on the surface, a friction coefficient is high, which presents a problem that an insertion force is large at the time of connection to a mating terminal. Particularly, in the case of using the terminal by incorporating the terminal into a connector, a multipole structure using a plurality of terminals is employed in many cases, wherefore a terminal insertion force tends to increase as the number of the terminals increases. To solve this problem, the present application discloses a technique of forming an alloy-containing layer made of Sn and Pd (palladium) and containing a Sn—Pd alloy on a base material made of copper or copper alloy (patent literature 2 WO2013/168764). A connector plated terminal having such a configuration can reduce a terminal insertion force at the time of connection to a mating terminal more than before.